title: Peripheral organ doses from radiotherapy for heterotopic ossification of non-hip joints: is there a risk for radiation-induced malignancies?
abstract: Radiotherapy, used for heterotopic ossification (HO) management, may increase radiation risk to patients. This study aimed to determine the peripheral dose to radiosensitive organs and the associated cancer risks due to radiotherapy of HO in common non-hip joints. A Monte Carlo model of a medical linear accelerator combined with a mathematical phantom representing an average adult patient were employed to simulate radiotherapy for HO with standard AP and PA fields in the regions of shoulder, elbow and knee. Radiation dose to all out-of-field radiosensitive organs defined by the International Commission on Radiological Protection was calculated. Cancer induction risk was estimated using organ-specific risk coefficients. Organ dose change with increased field dimensions was also evaluated. Radiation therapy for HO with a 7 Gy target dose in the sites of shoulder, elbow and knee, resulted in the following equivalent organ dose ranges of 0.85-62 mSv, 0.28-1.6 mSv and 0.04-1.6 mSv, respectively. Respective ranges for cancer risk were 0-5.1, 0-0.6 and 0-1.3 cases per 10(4) persons. Increasing the field size caused an average increase of peripheral doses by 15-20%. Individual organ dose increase depends upon the primary treatment site and the distance between organ of interest and treatment volume. Relatively increased risks of more than 1 case per 10,000 patients were found for skin, breast and thyroid malignancies after treatment in the region of shoulder and for skin cancer following elbow irradiation. The estimated risk for inducing any other malignant disease ranges from negligible to low.
authors.affiliation: University of Crete, Faculty of Medicine, Department of Medical Physics, P.O. Box 2208, 71003 Heraklion, Crete, Greece. Electronic address: theocharisberris@gmail.com.
authors.forename: Theocharis
authors.initials: T
authors.lastname: Berris
authors.affiliation: University of Crete, Faculty of Medicine, Department of Medical Physics, P.O. Box 2208, 71003 Heraklion, Crete, Greece. Electronic address: mazonak@med.uoc.gr.
authors.forename: Michalis
authors.initials: M
authors.lastname: Mazonakis
authors.affiliation: University Hospital of Heraklion, Department of Radiotherapy and Oncology, P.O. Box 1352, 71110 Heraklion, Crete, Greece. Electronic address: leukisgr@yahoo.com.
authors.forename: Stefanos
authors.initials: S
authors.lastname: Kachris
authors.affiliation: University of Crete, Faculty of Medicine, Department of Medical Physics, P.O. Box 2208, 71003 Heraklion, Crete, Greece. Electronic address: John.Damilakis@med.uoc.gr.
authors.forename: John
authors.initials: J
authors.lastname: Damilakis
mesh_terms: D000328:Adult; D006801:Humans; D009010:Monte Carlo Method; D009381:Neoplasms, Radiation-Induced; D009999:Ossification, Heterotopic / Q000532:radiotherapy*; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D012306:Risk
keywords: Cancer risk; Heterotopic ossification; Monte Carlo simulation; Radiotherapy